At present, studies are being undertaken to investigate the remodelling response to rotational malalignment in growing femurs of three month old puppies. This investigation proposes to extend that study to examine the morphologic response, not only in the femur but in the acetabulum proximally and the tibia distally following either distal femoral rotational osteotomy, or operatively produced paralysis of either the internal or extenal rotator muscles of the hip. Methods are described to investigate by radiographic and histologic means the specific morphologic response in those areas to the malrotation produced. It is hoped that this information will further add to the clinician's understanding of torsional remodelling in the growing femur following fracture, osteotomy, or in response to paralytic disorders about the hip.